As recently published on the avast! blog, modified versions of FileZilla tainted with malware are being distributed on some third-party websites.

This is by no means a new threat. While this instance is one of the largest to date, there have been many cases of modified versions spreading malware hosted on third-party websites for over a decade. We do not condone these actions and are taking measures to get the known offenders removed. Note that we cannot in general prevent tainted versions on third-party websites or prove their authenticity, especially since the FileZilla Project promotes beneficial redistribution and modifications of FileZilla in the spirit of free open source software and the GNU General Public License.